Sift the flour with the baking powder.
Heat a medium-pot to low temperature and add the butter, stir until it melts. Add the water, salt and sugar.
Add the flour mixture and stir with a wooden spoon, mixing constantly until the dough starts to separate from the pot and you see a fine film of dough covering the bowl.
Transfer the mixture to a bowl and add the eggs, one at the time, mixing with an electric mixer. Add the lemon zest.
Heat the oil in a pot at 180ºC.
Scoop the batter forming irregular 1 inch sized balls, transferring them directly to the hot oil and moving them constantly to get a round shape. Fry them until they are golden brown.
Transfer the buñuelos to a dish with kitchen towels to remove excess oil.
Top with a bit of powdered sugar.